Hit the switch and follow the caged hallway crossing an intersection and turning left at the end. After eliminating the cacodemons, flip the switch and go back into a new access at the corner. When you have dispatched the imps, get the red keycard and go back to the hallways. Return to the intersection, go west and enter the red door.

Cross the pool of lava and climb the stairs. Watch out for the baron of Hell who will be in a small raising section. Get the blue keycard and retrace your steps back out the red door. Follow the whole walkway until you arrive in a huge room with a curved walkway above another pool of lava. Watch for cacodemons to rise from there and follow the walkway to the blue door.

In the outdoor area, make your way around the walkway to a platform with a yellow keycard. Retrace your way back through the huge room and back into the caged hallways. At the intersection, go back north, around the corner and enter the yellow door near the switch you hit for the red keycard. Jump in the hole to exit.

At the level start, immediately turn around and open the wall behind you to reveal a secret area. (sector 29) A caged walkway has two medikits and an energy cell at its end, but the area is also occupied by monsters so beware.

Return to the starting room and press the switch. Once the floor lowers, open the vented wall to the right to access another fairly extensive secret area. (sector 34) Grab the backpack. At the top of the lift to the north, open a secret door with a different wall panel to get near the intersection. Alternatively, you can reach the lift area by taking the teleporter on the bottom of the nukage pool in the red keycard room. However, it is not the way to reach the backpack area that has the trigger for the secret credit.

Press the switch in secret #3 and return to the previous, lava-floored room. Two timed lifts have been lowered on the north and south walls. Ride the northern lift up into an alcove containing a combat armor vest. One of the walls in this alcove is differently textured from the rest. (sector 121) Open it and follow the tunnel to a soul sphere.The southern lift leads to a switch which is an alternative (somewhat pointless) way to access secret #1.

The caged walkway in secret #1 (see above) is surrounded by a huge moat of green nukage which has a radiation shielding suit and two teleporters on its bottom. One of the teleporters takes you atop the tallest of the three pillars overlooking the walkway. From there, you can run onto the top of a lower pillar to grab the plasma gun and then return to the walkway. The other teleporter warps you to the third pillar containing an energy cell pack.

West of the intersection, the southern wall has a part with pipes on it. Press it to open a secret door to the high nukage cavern. On Hurt me plenty or lower, there is a radiation suit so get it as soon as possible. There is a ledge that is overlooked by a higher outdoor area. In addition to the barrels, the ledge has the rocket launcher. Once you have grabbed the weapon, press the lion-head switch nearby to temporarily open a door back to the hallways.

The lift area mentioned in official secret #2 has another hidden door. When the lift is lowered, a door in the southeast corner can be entered and another lift can be discovered beyond it. Once you are at the top of the new lift, a room with the chaingun and a box of rockets is found. When you walk over the thin platform there, a door to the east will open revealing a chaingunner on Hurt me plenty or higher and two medikits. The two gargoyle-faces open a door back to the starting room. There is yet another teleporter that takes you to the outdoor area that overlooks the nukage cavern and holds a partial invisibility sphere. Exit the area using the same way as in the previous secret.

There is a teleporter on the bottom of the lava pool in the yellow keycard area. It takes the player back to the northern end of the curved walkway, allowing them to shave a few seconds off their time after the keycard has been obtained.